Control apparatus



Aug. 2, 1960 K. H. BECK CONTROL APPARATUS Filed July 11, 1956 IFIG.2

FIG.

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DIRECTION OF MISSILE TRAVEL INVENTOR. KENNETH H. BECK BY 2 Z ATTORNEY.

United States Patent CONTROL APPARATUS Kenneth H. Beck, Newtown, Pa., assignor to Minneapolis- Honeywell Regulator Company, Minneapolis, Minn, a corporation of Delaware Filed July 11, 1956, Ser. No. 597,273

Claims. (Cl. 317-1485) A general object of the present invention is to provide a new and improved control circuit. More specifically, the present invention is concerned with a circuit for operating an electromagnetic relay after a specified time delay.

In control applications it is frequently desirable to provide a specified time interval between the occurrence of a control signal and the operation of a. final control element such as an electromagnetic relay. For many applications, the apparatus designed to provide such a time delay must also be operative to prevent the operation of the final control element if the control signal is lost during the time delay. In addition, it is generally desirable that the circuit again be operative to initiate the specified time delay upon regaining the control signal. Accordingly, it is a specific object of the-present invention to provide a new and improved control circuit capable of providing such operation and yet characterized by simplicity and ruggedness of construction.

Another object of the present invention is to provide a time delay circuit in which the time delay is determined by the charging time of the capacitor which is charged to a voltage limited by a Zener diode.

Still another object of the present invention is toemploy a transistor to isolate the final control relay from the timing circuit, said transistor being controlled by the current passed by a Zener diode when the breakdown voltage of the diode is exceeded by the voltage across the capacitor in the timing circuit.

A further object of the present invention is to provide a new and improved time delay circuit with temperature compensation for the timing capacitor.

Another further object of the present invention is to provide a new and improved time delay circuit adapted to include voltage regulating means whereby the delay time is made relatively independent of the circuit energizing voltage.

A still further object of the present invention is to provide a time delay circuit particularly adapted for use-in missiles to control the arming of the missile warhead.

The various features ornovelty which characterize this invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its advantages,

and the specific objects obtained with its use, reference should be had to the accompanying drawings and descriptive matter in which are illustrated and described preferred embodiments of this invention.

Of the drawings:

Fig. l is a circuit diagram of a preferred embodiment of the present invention; v Fig. 2 is a circuit diagram of a modification of the embodiment of the present invention shown in Fig. 1 including Voltage regulating means provided to make the ,delay time substantially independent of the circuit energizing voltage; and

Fig. 3 shows an accelerometer switch used in conjunction with the time delay circuit of the present invention.

Referring now to Fig. 1, there is shown a circuit diagram of a preferred embodiment of the present invention operative to control the operation of the final control relay 1 after a specified time delay. The numeral 2 designates a terminal adapted to be connected to the positive terminal of a source of circuit energizing voltage. Similarly, the numeral 3 designates a terminal adapted to be connected to the negative terminal of the source of circuit energizing voltage. The operation of the circuit of Fig. 1 is controlled by means of a relay 4 connected in series with a pair of contacts 5 across the terminals 2 and 3. The relay 4 has associated therewith a stationary contact 6, a stationary contact 7, and a movable contact 8. The movable contact 8 of the relay 4 engages the stationary contact 6 when the relay 4 is energized and engages the contact 7 when the relay 4 is deenergized. The time delay in the present circuit is provided by means of a series connected RC circuit generally designated by the numeral 9. The time delay circuit 9 is connected across the terminals 2 and 3 and comprises a resistor 11, a thermistor 12 shunted by means of a resistor 13, the stationary contact 6 of the relay 4, the movable contact 8 of the relay 4, and a capacitor 14. As shown, the-stationary contact 7 of the relay 4 is connected by means of a conductor 15 to the terminal 3.

The load or controlled relay 1 is isolated from the time delay circuit by means of a transistor 17. The transistor 17 isan npn junction transistor having the usual emitter, collector, and base electrodes. The collector 18 of the transistor 17 is connected through the relay 1 to the terminal 2 and the emitter 19 of the transistor 17 is connected to the terminal 3. The base 21 of the transistor '17 is connected to the capacitor 14 by means of a Zener diode 22. The Zener diode 22 is poled to be reverse biased by the voltage across the capacitor 14.

In considering the operation of the circuit of Fig. l, the characteristics of Zener diodes should be understood. In the forward direction of current flow the resistance of these elements is low and current increases at the usual exponential rate with increases in the voltage applied across them. In the reverse direction their resistance is high until the breakdown voltage is exceeded, whereupon, current flow through them is substantially independent of further increases in the voltage applied across them. Accordingly, they are excellent voltage regulating devices.

The relay 4 is energized upon the closing of thecontacts 5. When the relay 4 is energized the movable contact 8 engages the stationary contact 6 which connects the capacitor 14 in series with the resistor 11 in the parallel combination of the thermistor 12 and the resistor 13 across the terminals 2 and 3. The capacitor 14 then charges at a rate determined by the time constant of the timing circuit. The capacitor 14 charges at this rate until the voltage across the capacitor 14 is equal to the breakdown voltage of the Zener diode 22 and the very small voltage drop across the base-emitter circuit of the .transistor 17. When the voltage across the capacitor 14 is equal to the breakdown voltage of the Zener diode22, current will begin to flow into the emitter-base circuit of the transistor 17. As the voltage across the capacitor 14 continues to increase, the transistor base current iricreases and hence the transistor collector current will increase until the final control relay 1 is energized. The relay 1 will remain energized as long as the contacts 5 are closed. Proper design enables the greatest part of the time delay to be controlled by the RC time constant prior to the time when the capacitor voltage equals the Zener diode breakdown voltage.

The thermistor 12 and the shunt respect to the resistor teristics of the capacitor vided by that network 13 are selected with 11 and the temperature charac- 14 such that the time delay prois independent of temperature variations in the capacitor '14 over a fairly wide range. Accordingly, in the construction of the-circuit of Fig. 1 the thermistor 12 is positioned so as to be subjected to the same ambient temperature conditions as the capacitor 14.

It should be noted that if the contacts are opened any time during the time delay interval the relay 4 will be deenergized and the charge accumulated on the capacitor 14 will be discharged through the movable relay contact 8, the stationary relay contact 7 and the conductor 15. If the contacts 5 are subsequently closed the circuit of Fig. 1 will be in condition to again start the time delay operation. Similarly, opening of the switching contacts 5 at any time after the final control relay 1 has been energized will cause that relay to be de energized due to the loss of control current flow into the transistor 17 from the capacitor 14. It should also be noted that if it is desired to have the contacts of the relay 5 remain closed once the relay 5 has been energized despite a subsequent opening of the switching contacts 5, a latching type relay could be employed for the relay :1. such a case, the relay 1 would have to be reset before the next timing operation.

The circuit of Fig. 1 is designed to provide a reliable time delay circuit for controllingthe operation of a relay which is characterized by simplicity of construction and rugged components. The use of the Zener diode 22 to control the. charging of the capacitor 14 provides a novel and reliable method of controlling the time delay. The temperature compensation provided by the thermistor 12 insures accurate circuit operation over a wide range of temperature. The, transistor 17 isolates the load relay 1 from the timing circuit and provides positive relay action when the voltage across the capacitor 14 reaches the breakdown voltage of the Zenerdiode 22.

Referring now to Fig. 2, there is shown a circuit dia gram of a modification of the circuit shown in Fig. v1. This modification provides a voltage regulating network designed to make the time delay independent of the sup.- ply voltage. Similar reference characters have been employed to designate components similar to those employed in Fig. 1'. In this circuit, voltage regulation is supplied by the Zener diode 31 which is connected in series. with a resistor 32 across the terminals 2 and, 3. As: shown, the time delay network 9 is -connected between the junction 33 of the resistor 32 and the Zener diode 31 and the terminal 3:. Due to the characteristics of the Zener diode 3 1, a voltage across the time delay network will be substantially constant despite small variations in the supply voltage.

Referring now to Fig. 3, there is shown a sectional view of an accelerometer switch 41 used in conjunction with the time delay circuit of the present invention. The time delay circuit is generally designated 42. The accelerometer switch 41 in combination with the time delay circuit 42 is. operable to achieve the arming of a missile warhead when the missile reaches. a predetermined acceleration. Upon reaching that predetermined acceleration, the hemispherical contacts of the switch are engaged, at which time the time delay circuit will effect the, missile arming operation only if the contacts of the switch are engaged and remain in continuous contact with one another for a predetermined period of time.

The accelerometer switch 41 comprises an integral hollow member having a cylindrical portion 43', and a hemispherical portion 44. Suitable struts 45 and 46 are, connected at their inner ends to the cylindrical outer surface of the portion 43. and are connected attheir outerends to the interior of the guided missile. 47. An insulating sleeve 48. lines a section of the interior wall of the cylindrical portion 43. An electrical contact surface 50 lines the hemispherical portion 424 and is. insulated. therefrom by a layer of suitable insulating. material 491 A suitably insulated connection 51 provides the means for making the electrical connection to the contact 4 surface 50 through the hemispherical portion 44 of the accelerometer switch.

The numeral 55 designates an inner gimbal ring which is pivotally connected to an end portion of the cylindrical part 43 by means of a pivot 56 and a second pivot parallel therewith but not shown in this view. This inner ring 55, in turn, supports the ends of a hollow telescopic guide member 58 by means of the pivots 57 and 57'. The inner gimbal ring 55 has connected thereto one end of a coil spring 59 and one end of a coil spring 61. The other ends .of the coil springs 59 and 61 are connected by means of suitable lugs 62 and 63 to a solid hemispherical contact 64. As shown, the flat end of the hemispherical contact =64 is integrally connected to a hollow sleeve member 65 that is slidably supported in the guide 58. The guide 58 and the sleeve 65 are used as slidable conductors to complete an electrical circuit to the contact 64. An electrical connection 66 is shown connected to the telescopic guide member 58 in the furtherance of the electrical connection. It should here be noted, that the hemispherical contact 64 and the hemispherical contact surface 50 comprise the switching contact 5 shown in Figs. 1 and 2.

The dot-dash line 67 shows how an outer peripheral point on the hemispherical contact 64 will be brought into contact with the contact surface 50 when the missile 47 is accelerating at some predetermined value in the di rest-ion of the arrow shown in the drawing. Numerals 68 and 69 which are indicated in the dot-dash line form shown, represent other positions which the hemispherical contact .64 will be moved to when the aforementioned acceleration of the missile is attained and the missile is going in directions other than that shown by the arrow in the drawing.

Fig. 3 also shows how some of the chief components of the time delay circuit of Fig. 1 may be located with respect to the accelerometer switch. The relay 4is shown mounted in the interior of the telescopic guide member 65. The final control arming relay 1, variable resistance 11, the capacitor 14, and the transistor 17 are all schematically shown as being located to the right of the accelerometer switch.

In considering the operation of the accelerometer switch shown in Fig. 3, it should be noted that when the missile is accelerating in an angular direction, the solid hemispherical contact 24 will be caused to move outwardly to the right of the position shown in that figure by the acceleration force acting on the contact 64. Since the telescopic guide 58 is mounted by means of the gimbal ring 55 and moves about the axis pivot 16, the contact member 64 will be caused to move not only to the right of the position shown but in a slightly downward angular direction. When a preset acceleration such as, for example, three times the pull of gravity is reached, the hemispherical contact 64 will be brought into point engagement with the contact surface 50. Should the acceleration of the missile drop below the necessary preset acceleration level after the contact member 64 has been in engagement with the contact surface 50, the force of the springs then in tension will be sufficient to withdraw the contact 64 to the left and out of contact with the contact surface 50.

Because the contact 64 is caused to move in a hemispherical manner alongthe contact surface while the missile is changing its direction from a vertical to a horizontal position, this apparatus will cancel out any errors due to changes in the gravitational force acting on the missile when such changes in missile direction occtu.

From the foregoing, it can be seen that the accelerometer switch shown in the Fig. 3 may be combined with. the the time delay circuit of the present invention to. efilect a missile arming operation when the missile has accelerated ata predetermined acceleration for a predetermined period of time. If it is desired to. have the missile remain armed after once having been armed,

despite a subsequent loss of acceleration, relay can be employed for the relay 1 as inbefore.

Subject matter disclosed but not claimed herein is being disclosed and claimed in the copending application of Chung Liao Feng and Robert E. Ochs, Jr. Serial No. 597,283 filed on even date herewith and assigned to the same assignee, now Patent No. 2,851,554.

While, in accordance with the provisions of the statutes, there has been illustrated and described the best form of the invention now known, it will be apparent to those skilled in the art that changes may be made in the form of the apparatus disclosed without departing from the spirit of the invention as set forth in the appended claims, and that in some instances certain features of the invention may be used to advantage without a corresponding use of other features.

Having now described my invention, what I claim as new and desire to secure by Letters Patent is:

1. A time delay relay control circuit comprising, in combination, a first terminal adapted to be connected to the positive terminal of a source of voltage, a second terminal adapted to be connected to the negative terminal of said source of voltage, a circuit control relay and a pair of switching contacts for controlling the energization of said relay connected across said first and second terminals, said relay having associated therewith a first stationary cont-act, a second stationary contact, and a movable contact, said movable contact engaging said first stationary contact when said relay is energized and engaging said second stationary contact when said relay is deenergized, a timing circuit connected across said terminals and comprising a first resistor, a thermistor and a second resistor connected in parallel, said first stationary contact, said movable contact, and a capacitor, the temperature characteristics of said thermistor as shunted by said second resistor being such as to substantially conmpensate for changes in said capacitor due to temperature, said second stationary contact and said capacitor being connected to said second terminal, a load relay, a transistor having an emitter, a collector, and a base, the collector of said transistor being connected through said load relay to said first terminal, the emitter of said transistor being connected to said second terminal, and a Zener diode connected between said capacitor and the base of said transistor and poled to be reverse biased by the voltage across said capacitor.

2. A time delay relay control circuit comprising, in combination, a first terminal adapted to be connected to the positive terminal of a source of voltage, a second terminal adapted to be connected to the negative terminal of said source of voltage, a circuit control relay and a pair of switching contacts for controlling the energization of said relay connected across said first and second terminals, said relay having associated therewith a first stationary contact, a second stationary contact, and a movable contact, said movable contact engaging said first stationary contact when said relay is energized and engaging said second stationary contact when said relay is deenergized, a voltage regulating circuit comprising resistor means and a first Zener diode connected in series across said terminals, a timing circuit connected between the junction of said resistive means and said Zener diode and said second terminal, said timing circuit comprising a first resistor, a thermistor and a second resistor connected in parallel, said first stationary contact, said movable contact, and a capacitor, the temperature characteristics of said thermistor as shunted by said second resistor being such as to substantially compensate for changes in said capacitor due to temperature, said second stationary contact, and said capacitor being connected to said second terminal, a load relay, a transistor having an emitter, a collector, and a base, the collector of said transistor being connected through said load relay to said first terminal, the emitter of said transistor being cona latching type explained here- 6 nected to said second terminal, and a second Zener diode connected between said capacitor and the base of said transistor and poled to be reverse biased by the voltage across said capacitor.

3. An apparatus for operating a load relay when said apparatus is subjected to a predetermined acceleration and that acceleration is maintained for a predetermined time comprising, in combination, a first terminal adapted to be connected to the positive terminal of a source of voltage, a second terminal adapted to be connected to the negative terminal of said source of volt-age, a circuit control relay and a pair of acceleration sensitive switching contacts for controlling the energization of said circuit control relay connected across said first and second terminals, said switching contacts being adapted to cause said circuit control relay to be energized upon the occurrence of said predetermined acceleration, said circuit control relay having associated therewith a first stationary contact, a second stationary contact, and a movable contact, said movable contact engaging said first stationary contact when said circuit control relay is energized and engaging said second stationary contact when said circuit control relay is deenergized, a timing circuit connected across said terminals and comprising a first resistor, a temperature sensitive resistance and a second resistor connected in parallel, said first stationary contact, said movable contact, and a capacitor, the temperature characteristics of said resistance as shunted by said second resistor being such as to substantially compensate for changes in said capacitor due to temperature, said second stationary contact and said capacitor being connected to said second terminal, a load relay, a transistor having an emitter, a collector, and a base, the collector of said transistor being connected through said load relay to said first terminal, the emitter of said transistor being connected to said second terminal, and a Zener diode having a predetermined breakdown voltage connected between said capacitor and the base of said transistor and poled to be reverse biased by the voltage across said capacitor, the capacity of said capacitor and the resistance of said timing circuit being so proportioned that said voltage across said capacitor reaches said breakdown voltage of said Zener diode at said predetermined time.

4. A time delay relay control circuit comprising, in combination, a first terminal adapted to be connected to the positive terminal of a source of voltage, a second terminal adapted to be connected to the negative terminal of said source of voltage, a circuit control relay and a pair of switching contacts for contolling the energization of said relay connected across said first and second terminals, said relay having associated therewith a first stationary contact, a second stationary contact, and a movable contact, said movable contact engaging said first stationary contact when said relay is energized and engaging said second stationary contact when said relay is deenergized, a timing circuit connected across said terminals and comprising a first resistor, a temperature sensitive resistance and a second resistor connected in parallel, said first stationary contact, said movable contact, and a capacitor, the temperature characteristics of said temperature sensitive resistance shunted by said second resistor being such as to substantially compensate for changes in said capacitor due to temperature, said second stationary contact and said capacitor being connected to said second terminal, a load relay, a transistor having an emitter, a collector, and a base, the collector of said transistor being connected through said load relay to said first terminal, the emitter of said transistor being connected to said second terminal, and a Zener diode connected between said capacitor and the base of said transistor and poled to be reverse biased by the voltage across said capacitor.

5. A time delay relay control circuit comprising, in combination, a first terminal adapted to be connected to the positive terminal of a source of voltage, a second terminal adaptedtov be connected. to the negative terminal of, said source of voltage,; a circuit control relay and a pain of switching-contacts for-controllingthe energiz-ation of said relay connected across said fi rst and second terminals, said relay. having: associated therewith a first stationary contact, a second stationary contact, and a movable contact, said movable contactengaging said first stationary contact when said relay is energized and engaging said. second stationary contact when said relay is deenergized, a voltage regulating circuit comprising resistor means and aifirst Zener diode connected in series across'said terminals, atiming circuitconnected between the junction of said resistive means and saidZener diode and saidsecond terminal, said timing circuit comprising a first resistonatemperature sensitive resistance anda second resistor connected in parallel, said first stationary contact, said movable contact, and a capacitor, the temperature characteristics of said temperature sensitive resistance as shunted by said. second resistor being such as to substantially compensate for changes in said capacitor due to temperature, said second stationary contact and said capacitor being connected to said second second-terminal, and a second Z'ener diode connectedbetween saidcapacitorand the base of' said: transistor and poled to be reverse biased by the voltage across said capacitor.

References Cited in the fileof this patent UNITED STATES PATENTS 1,917,418 Alm'quist July 11, 1933 2,584,990 Dimond Feb.- 12, 1952; 2,615,967- Gould Oct. 28, 1952'- 2',621,808 Blakeney Dec. 16, 1952 2,693,572 Chase Nov; 2, 1954 2,769,131 Immel Oct. 30,1956 OTHER REFERENCES Publication"Transistorized Headlight Dimmer, pages 56, 57, 122, of Radio and Television News magazine of August 1955. 

